Improvements to Schur template specializations

1. Refactor the python code that generates the template specializations
   to remove code duplication.
2. Improved the logic for template specialization selection where
   Eigen::Dynamic now serves as a wildcard.
3. Added schur_templates.h/cc which allows querying the set of available
   template specializations without instantiating a linear solver.
4. Added Solver::Summary::schur_structre_given and
   Solver::Summary::schur_structure_used and expose them in
   Solver::Summary::FullReport for better performance debugging.
5. Updated the templates with newer dates and some minor comments cleanup
   which lead to the the template specializations to be re-generated.

Change-Id: Iaf3c6f714353597899916c300465da01f151c3de